chore(ingestion): Break out routing normalization PR for posthog (capture.py) only

[eli-r-ph]

Problem

We'd like to normalize all the event drop and rerouting (overflow etc.) across ingest services so this functionality is easier to use for maintainers.

Changes

Extracted the Python-specific (Django capture) changes from this closed PR.

🎗️ Will require a matching charts change to shift preexisting settings to the new var and format.

Does this work well for both Cloud and self-hosted?

Yes

How did you test this code?

Locally and in CI

[nickbest-ph]

Is there a corresponding charts PR that needs to go out first? Or is this env var already set on the django pods?

[eli-r-ph]

I need to check on that since the naming is changed but I assume yes on the charts deploy - noted in the PR desc as well 👍

[pl]

LGTM, do we have any dropped tokens in django capture on prod?

[pl]

Also, I don't think any of the test failures are related to your changes.

[greptile-apps]

PR Summary

This PR normalizes event dropping functionality in PostHog's ingestion services by renaming environment variables and modifying token/distinct ID pair handling.

• Changed environment variable from DROPPED_KEYS to DROP_EVENTS_BY_TOKEN_DISTINCT_ID in /posthog/settings/ingestion.py for clearer intent
• Modified delimiter from semicolon to comma for token:distinct_id pairs in /posthog/api/capture.py
• Made distinct_id optional in token:distinct_id pairs for more flexible event dropping
• Reorganized Kafka topic imports in /posthog/api/capture.py for better code organization

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[nickbest-ph]

lgtm

[eli-r-ph]

👋 working up corresponding PR to ensure the deployed env vars are set to expect this change

[eli-r-ph]

I couldn't find any reference to DROPPED_KEYS env var in deployment repo so I think we're gtg here